46. Client-side vs Server-side rendering?
Client-side: Rendering in browser via JavaScript.
Server-side: HTML generated on server before sending.
47. Explain the DOM.
The Document Object Model represents HTML as a tree structure that JavaScript can manipulate.
48. What is AJAX?
Asynchronous JavaScript and XML — allows updating page content without reloading.
49. What is CORS?
Cross-Origin Resource Sharing — controls which domains can access APIs.
50. localStorage vs sessionStorage?
localStorage persists until manually cleared.
sessionStorage clears when tab closes.
51. How do you optimize front-end performance?
- Minify CSS/JS
- Lazy loading
- Caching
- CDN usage
- Reduce HTTP requests
52. What are HTTP status codes?
200 OK
201 Created
400 Bad Request
401 Unauthorized
403 Forbidden
404 Not Found
500 Server Error
53. What is JSON?
Lightweight data-interchange format used in APIs.
54. What is responsive design?
Design that adapts to different screen sizes using CSS media queries.
55. PUT vs PATCH?
PUT replaces entire resource.
PATCH partially updates resource.